1. Technical Field
This invention relates to process for producing a tape scraper having a pair of edges, in which the pair of edges are formed linearly in parallel with each other.
2. Prior Art
For a magnetic record/playback device, it is required to remove any dust stuck on a recording surface of a magnetic tape, so that a tape scraper having a pair of edges contacting the recording surface of magnetic tape is disposed in a running route of the magnetic tape. According to this kind of tape scraper, in order that the magnetic tape may run without twisting between the pair of edges and any dust stuck on the recording surface may be removed effectively, the pair of edges must be disposed in parallel with other in the running route of magnetic tape, positioning in a perpendicular state relative to a running direction of magnetic tape.
FIG. 7 shows an example of a conventional tape scraper, in which a tape scraper 40 comprises a nearly U-shape sectioned base block 41 and a pair of knife edge members 50 and 60 fixed on cutaway portions 44 and 45 formed on opposing walls 42 and 43 of base block 41. A bottom surface 41.sub.1 of base block 41 is positioned in the running route of magnetic tape T mounted on a main chassis 70, on which a magnetic head (not illustrated) is disposed. Accordingly, if magnetic tape T is running in a rightward direction in FIG. 7, any dust or the like stuck on the recording surface of magnetic tape T are removed by an edge 61 of a knife edge member 60 located in the downstream direction. On the other hand, if magnetic tape T is running in a leftward direction in FIG. 7, dust and the like are removed by an edge 51 of knife edge member 50.
Now, a process for producing tape scraper 40 is discussed. As shown in FIG. 8(a), a nearly U-shape sectioned base block 41 is prepared by grinding a prismatic material made of, for example, aluminum. As used herein, the word "prismatic" is taken to mean a body having top and bottom surfaces that are generally parallel to each other. Such a body may be, for example, a paralleliped. Bodies having more or less than four surfaces, and with non-parallel surfaces should not be excluded from the definition.
Subsequently, as shown in FIG. 8(b), cutaway portions 44 and 45 are formed upon opposing walls 42 and 43 perpendicular to bottom surface 41.sub.1.
Referring to FIG. 8(c), a prismatic bar 52 made of a hard non-magnetic material such as, for example, sapphire, ceramic or the like is ground to remove sides 52.sub.1 and 52.sub.2, to form knife edge member 50. Similarly, sides 62.sub.1 and 62.sub.2 are removed from a prismatic bar 62 to form knife edge member 60.
Further, surfaces 50.sub.1 and 50.sub.2, and 60.sub.1 and 60.sub.2, formed by removing sides 52.sub.1 and 52.sub.2, and 62.sub.1 and 62.sub.2, respectively are lapped to provide a mirror finish. Then, knife edge members 50 and 60 are installed in cutaway portions 44 and 45, respectively using, for example, a suitable adhesive, to form the finished tape scraper 40 as shown in FIG. 7.
However, according to the foregoing conventional process, base block 41, knife edge members 50 and 60, having edges 51 and 61, respectively, are formed as separate components which are then united into a unitary tape scraper 40 using a suitable adhesive. As a result of an unbalanced thickness of the adhesive layer or some manufacturing inaccuracy of respective components, the parallelism of edges 51 and 61 may be unsatisfactory. In addition the accuracy with which edges 51 and 61 are maintained perpendicular degree to the running direction of magnetic tape T may not be satisfactory.